Some power plant systems, for example certain nuclear, simple cycle and combined cycle power plant systems, employ turbines in their design and operation. Some of these turbines are driven by a flow of high temperature working fluid (e.g., steam, gas, etc.) which is directed over and/or through a series of stages and components (e.g., alternating stationary and rotary airfoils/buckets/blades) within the turbine to generate power. These components and stages may be located at close proximity (e.g., small clearances) relative to one another so as to decrease working fluid leakage through the system and improve turbine efficiency.
In some systems, working fluid may be contained within the flowpath and leaks reduced by passing a pressurized cooling fluid (e.g., compressor air) about the flowpath which is contained by a set of seals. Direct leakage of the pressurized cooling fluid into the flowpath and/or of the working fluid out of the turbine may reduce turbine efficiency and component and turbine lifespan. However, as a result of the high temperatures of the working fluid during operation, components (e.g., stators, blades, shells, etc.) may experience a significant increase in temperature, often rising across a temperature range of hundreds of degrees Celsius and resulting in thermal expansion which may require clearances between components which may cause leakage. As a result, some systems locate seals between segmented static turbine components (e.g., stator shells, shrouds, nozzles, gas path components, etc.). In most systems these seals are located away from the flowpath of the working fluid so as to reduce/limit exposure of the seal to the thermal extremes of the working fluid. This location however requires additional purge air to cool down the inter-segment chute region. Some other systems locate the seal at a closer proximity to the gas path, as a result these seals require active surface cooling to thermally withstand the impact of the hot working fluid flow proximate the seal surface. These seals may limit turbine design and operation, by requiring a large amount of coolant flow into the turbine system and subsequent leakage into the flowpath, thereby reducing turbine efficiency.